System for translation of electromagnetic and optical localization systems

ABSTRACT

A system for utilizing and registering at least two surgical navigation systems during stereotactic surgery. The system comprises a first surgical navigation system defining a first patient space, a second surgical navigation system defining a second patient space, and a translation device to register the coordinates of the first patient space to the coordinates of the second patient space. The translation device comprises a rigid body, at least one component for a first navigation system placed in or on the rigid body, and at least one component for a second navigation system placed in or on the rigid body, in known relation to the at least one component for the first navigation system. The translation device is positioned in a working volume of each of the at least two navigation systems.

CONCURRENTLY FILED APPLICATIONS

[0001] The following United States patent applications, which wereconcurrently filed with this one on Oct. 28, 1999, are fullyincorporated herein by reference: Method and System for Navigating aCatheter Probe in the Presence of Field-influencing Objects, by MichaelMartinelli, Paul Kessman and Brad Jascob; Patient-shielding and CoilSystem, by Michael Martinelli, Paul Kessman and Brad Jascob; NavigationInformation Overlay onto Ultrasound Imagery, by Paul Kessman, TroyHolsing and Jason Trobaugh; Coil Structures and Methods for GeneratingMagnetic Fields, by Brad Jascob, Paul Kessman and Michael Martinelli;Registration of Human Anatomy Integrated for ElectromagneticLocalization, by Mark W. Hunter and Paul Kessman; System for Translationof Electromagnetic and Optical Localization Systems, by Mark W. Hunterand Paul Kessman; Surgical Communication and Power System, by Mark W.Hunter, Paul Kessman and Brad Jascob; and Surgical Sensor, by Mark W.Hunter, Sheri McCoid and Paul Kessman.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to localization of a positionduring surgery. The present invention relates more specifically to asystem that facilitates combined electromagnetic and opticallocalization of a position during stereotactic surgery, such as brainsurgery and spinal surgery.

[0004] 2. Description of Related Art

[0005] Precise localization of a position has always been important tostereotactic surgery. In addition, minimizing invasiveness of surgery isimportant to reduce health risks for a patient. Stereotactic surgeryminimizes invasiveness of surgical procedures by allowing a device to beguided through tissue that has been localized by preoperative scanningtechniques, such as for example, MR, CT, ultrasound, fluoro and PET.Recent developments in stereotactic surgery have increased localizationprecision and helped minimize invasiveness of surgery.

[0006] Stereotactic surgery is now commonly used in surgery of thebrain. Such methods typically involve acquiring image data by placingfiducial markers on the patient's head, scanning the patient's head,attaching a headring to the patient's head, and determining the spatialrelation of the image data to the headring by, for example, registrationof the fiducial markers. Registration of the fiducial markers relatesthe information in the scanned image data for the patient's brain to thebrain itself, and utilizes one-to-one mapping between the fiducialmarkers as identified in the image data and the fiducial markers thatremain on the patient's head after scanning and throughout surgery. Thisis referred to as registering image space to patient space. Often, theimage space must also be registered to another image space. Registrationis accomplished through knowledge of the coordinate vectors of at leastthree non-collinear points in the image space and the patient space.

[0007] Currently, registration for image guided surgery is completed bya few different methods. First, point-to-point registration isaccomplished by the user to identify points in image space and thentouch the same points in patient space. Second, surface registrationinvolves the user's generation of a surface (e.g., the patient'sforehead) in patient space by either selecting multiple points orscanning, and then accepting or rejecting the best fit to that surfacein image space, as chosen by the processor. Third, repeat fixationdevices entail the user repeatedly removing and replacing a device inknown relation to the fiducial markers. Such registration methods haveadditional steps during the procedure, and therefore increase thecomplexity of the system and increase opportunities for introduction ofhuman error.

[0008] Through the image data, quantitative coordinates of targetswithin the patient's body can be specified relative to the fiducialmarkers. Once a guide probe or other instrument has been registered tothe fiducial markers on the patient's body, the instrument can benavigated through the patient's body using image data.

[0009] It is also known to display large, three-dimensional data sets ofimage data in an operating room or in the direct field of view of asurgical microscope. Accordingly, a graphical representation ofinstrument navigation through the patient's body is displayed on acomputer screen based on reconstructed images of scanned image data.

[0010] Although scanners provide valuable information for stereotacticsurgery, improved accuracy in defining the position of the target withrespect to an accessible reference location can be desirable.Inaccuracies in defining the target position create inaccuracies inplacing a therapeutic probe. One method for attempting to limitinaccuracies in defining the target position involves fixing thepatient's head to the scanner to preserve the reference. Such fixationmay be uncomfortable for the patient and creates other inconveniences,particularly if surgical procedures are involved. Consequently, a needexists for a system utilizing a scanner to accurately locate positionsof targets, which allows the patient to be removed from the scanner.

[0011] Stereotactic surgery utilizing a three-dimensional digitizerallows a patient to be removed from the scanner while still maintaininga high degree of accuracy for locating the position of targets. Thethree-dimensional digitizer is used as a localizer to determine theintra-procedural relative positions of the target. Three-dimensionaldigitizers may employ optical, acoustic, electromagnetic or otherthree-dimensional navigation technology for navigation through thepatient space.

[0012] Different navigational systems have different advantages anddisadvantages. For example, electromagnetic navigation systems do notrequire line-of-sight between the tracking system components. Thus,electromagnetic navigation is beneficial for laproscopic andpercutaneous procedures where the part of the instrument tracked cannotbe kept in the line-of sight of the other navigation system components.Since electromagnetic navigation allows a tracking element to be placedat the tip of an instrument, electromagnetic navigation allows the useof non-rigid instruments such as flexible endoscopes. However, use ofcertain materials in procedures employing electromagnetic tracking isdisadvantageous since certain materials could affect the electromagneticfields used for navigation and therefore affect system accuracy.

[0013] Comparatively, optical navigation systems have a larger workingvolume than electromagnetic navigation systems, and can be used withinstruments having any material composition. However, the nature ofoptical navigation systems does not accommodate tracking systemcomponents on any portion of an instrument to be inserted into thepatient's body. For percutaneous and laproscopic procedures, opticalnavigation systems typically track portions of the system componentsthat are in the system's line of sight, and then determine the positionof any non-visible portions of those components based on systemparameters. For example, an optical navigation system can track thehandle of a surgical instrument but not the inserted tip of the surgicalinstrument, thus the navigation system must track the instrument handleand use predetermined measurements of the device to determine where thetip of the instrument is relative to the handle. This technique cannotbe used for flexible instruments since the relation between the handleand the tip varies.

[0014] Stereotactic surgery techniques are also utilized for spinalsurgery, in order to increase accuracy of the surgery and minimizeinvasiveness. Accuracy is particularly difficult in spinal surgery andmust be accommodated in registration and localization techniquesutilized in the surgery. Prior to spinal surgery, the vertebra arescanned to determine their alignment and positioning. During imaging,scans are taken at intervals through the vertebra to create athree-dimensional pre-procedural data set for the vertebra. However,after scanning the patient must be moved to the operating table, causingrepositioning of the vertebra. In addition, the respective positions ofthe vertebra may shift once the patient has been immobilized on theoperating table because, unlike the brain, the spine is not heldrelatively still by a skull-like enveloping structure. Even normalpatient respiration may cause relative movement of the vertebra.

[0015] Computer processes discriminate the image data retrieved byscanning the spine so that the body vertebra remain in memory. Once thevertebra are each defined as a single rigid body, the vertebra can berepositioned with software algorithms that define a displaced image dataset. Each rigid body element has at least three fiducial markers thatare visible on the pre-procedural images and accurately detectableduring the procedure. It is preferable to select reference points on thespinous process that are routinely exposed during such surgery.

[0016] See also, for example, U.S. Pat. No. 5,871,445, WO 96/11624, U.S.Pat. No. 5,592,939 and U.S. Pat. No. 5,697,377, the disclosures of whichare incorporated herein by reference.

SUMMARY OF THE INVENTION

[0017] To enhance the prior art, and in accordance with the purposes ofthe invention, as embodied and broadly described herein, there isprovided a system for utilizing and registering at least two surgicalnavigation systems during stereotactic surgery. The system comprises afirst surgical navigation system defining a first patient space, asecond surgical navigation system defining a second patient space, and atranslation device to register the coordinates of the first patientspace to the coordinates of the second patient space. The translationdevice comprises a rigid body, at least one component for a firstnavigation system placed in or on the rigid body, and at least onecomponent for a second navigation system placed in or on the rigid body,in known relation to the at least one component for the first navigationsystem. The translation device is positioned in a working volume of eachof the at least two navigation systems.

[0018] Additional features and advantages of the invention will be setforth in the description which follows, and in part will be apparentfrom the description, or may be learned from practice of the invention.The objectives and other advantages of the invention will be realizedand attained by the apparatus particularly pointed out in the writtendescription and claims herein as well as the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated in andconstitute part of the specification, illustrate a presently preferredembodiment of the invention and together with the general descriptiongiven above and detailed description of the preferred embodiment givenbelow, serve to explain the principles of the invention.

[0020]FIG. 1 is a schematic diagram illustrating an embodiment of thesystem that facilitates combined electromagnetic and opticallocalization of a position during stereotactic surgery according to thepresent invention;

[0021]FIG. 2 illustrates a top view of a first embodiment of anoptical-to-electromagnetic translation device;

[0022]FIG. 3 illustrates a schematic perspective view of a secondembodiment of an optical-to-electromagnetic translation device;

[0023]FIG. 4 illustrates a schematic perspective view of a thirdembodiment of an optical-to-electromagnetic translation device; and

[0024]FIG. 5 illustrates a schematic perspective view of a fourthembodiment of an optical-to-electromagnetic translation device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Reference will now be made in detail to the present preferredexemplary embodiments of the invention, examples of which areillustrated in the accompanying drawings. Wherever possible, the samereference numbers will be used throughout the drawings to refer to thesame or like parts.

[0026] The present invention contemplates a system for stereotacticsurgery comprising a first surgical navigation system defining a firstpatient space, a second surgical navigation system defining a secondpatient space, a translation device to register (correlate thecoordinates of) the first patient space to the second patient space, andan image data set generated from a scanning device that defines an imagespace. The image space is registered to at least one of the first andsecond patient spaces.

[0027] An exemplary embodiment of the system 10 of the present inventionis illustrated in FIG. 1. The system of the present invention will bediscussed hereinafter with respect to a an optical navigation system incombination with an electromagnetic navigation system. However, thepresent invention similarly contemplates combining any two navigationsystems including optical, acoustic, electromagnetic, or conductive.

[0028] The system illustrated in FIG. 1 includes a first navigationsystem that is optical. Elements of the optical navigation systeminclude at least one optical element, and an optical receiving array 40in line-of-sight communication with the optical element and incommunication with a computer system 50. The optical element can eithergenerate an optical signal independently or alternatively generate anoptical signal by reflecting a signal received from an optical signalsource. The line-of-sight of the optical receiving array defines a“working volume” of the optical system, which is the space in which theoptical system can effectively navigate.

[0029] At least one optical element is placed on a translation device.According to the illustrated embodiment of the present invention,preferably at least three non-collinear optical elements are utilized bythe system in order to obtain six degrees of freedom location andorientation information from the optical elements.

[0030] In the exemplary embodiment of the invention illustrated in FIG.1, four embodiments of the translation device 20, 60, 80, 100 are shownin the working volume of the optical system. While only one translationdevice is needed for proper operation of the translation system of thepresent invention, the present invention also contemplates the use ofmore than one translation device for registration of differentnavigation systems. For example, more than one translation device couldbe used for redundant registration of two navigation systems in order toobtain increased accuracy of registration. In addition, if threedifferent navigation systems were utilized in a single surgicalprocedure, one translation device could be used to register (i.e.,correlate the coordinates of) all three navigation systems, or onetranslation device could be used to register the first and secondnavigation systems while another translation device registered thesecond and third navigation systems.

[0031] As illustrated in FIGS. 1 and 2, a dynamic translation device canbe incorporated into a medical instrument 60 for use in the surgicalprocedure being navigated. The medical instrument 60 includes a handle62, a tip portion 64 and a localization frame 66. At least threecollinear optical elements 70 (capable of defining six degrees offreedom in the optical system) are placed on the localization frame forcommunication with the optical receiving array 40. As the medicalinstrument moves in the working volume of the optical system, theoptical receiving array 40 sends a signal to the computer system 50indicating the current position of the medical instrument 60.

[0032] As illustrated in FIGS. 1 and 3, a translation device can also beincorporated into a rigid static translation device 100 that is added tothe optical and electromagnetic navigation system working spacesspecifically to register (i.e., correlate the coordinates of) theoptical navigation system to the electromagnetic navigation system. Thestatic translation device may have any configuration allowing opticalelements 110 to be placed in such a manner to define six degrees offreedom in the optical system (e.g., three non-collinear opticalelements). Although this embodiment provides a suitable translationdevice, it also adds undesirable complexity to the navigation systems byrequiring the navigation systems to receive input from and identify anadditional structure in their working volume.

[0033] As illustrated in FIGS. 1 and 4, a translation device can also beincorporated into the operating table. Optical elements 85 defining sixdegrees of freedom in the optical system are placed on the operatingtable in such a manner that they will remain in the line-of-sight of theoptical receiving array 40 during the procedure.

[0034] As illustrated in FIGS. 1 and 5, a dynamic translation device canfurther be incorporated into one or more of the optical elements 20placed on the patient 30 (or mounted to the patient via a frame).

[0035] It is to be understood that optical elements 20, 70 may be placedon the patient 30 or on the medical instrument 60 for tracking movementof the patient 30 and/or the medical instrument 60 during the procedure,even if the optical elements 20, 70 on the patient 30 and the medicalinstrument 60 are not used as translation devices.

[0036] As illustrated in FIG. 1, the system of the present inventionalso includes a second navigation system. In the embodiment illustratedin FIG. 1, the second navigation system is electromagnetic. Thus, anytranslation device also has at least one component for theelectromagnetic navigation system that is in known relationship to theoptical elements placed on the device. The known relation of the opticaland electromagnetic elements is received by the computer system 50 sothat the computer system can generate a translation matrix forregistration (i.e., correlation of the coordinates) of the optical andelectromagnetic navigation systems. Elements of the illustratedelectromagnetic navigation system include an electromagnetic element 90(e.g., a sensor having at least one coil 92), and a magnetic fieldgenerator. In the embodiment shown in FIG. 1, the magnetic fieldgenerator is provided in the operating table 80. Therefore, in theembodiment of the translation device shown in FIG. 4, as describedabove, the magnetic field generator in the operating table 80 serves asthe electromagnetic element on the translation device when placed inknown relation to the optical elements 85 placed on the table 80. Theknown relation of the optical and electromagnetic elements is receivedby the computer system 50 so that the computer system can generate atranslation matrix for correlation of the optical and electromagneticnavigation system coordinates.

[0037] In the medical instrument 60 embodiment of the translation deviceillustrated in FIG. 2, the electromagnetic element 90 is preferably asensor having at least one coil 92. The sensor includes two coils 92that are placed perpendicular to each other to create a sensor havingsix degrees of freedom. The sensor is placed in or on the localizationframe 66 in known relation to the optical elements 70. The knownrelation of the optical and electromagnetic elements is received by thecomputer system 50 so that the computer system can generate atranslation matrix for correlation of the optical and electromagneticnavigation system coordinates.

[0038] In the rigid static embodiment 100 of the translation deviceillustrated in FIG. 3, the electromagnetic element 90 is preferably asensor as described above with respect to FIG. 2, placed in or on therigid static device 100 in known relation to the optical elements 110.The known relation of the optical and electromagnetic elements isreceived by the computer system 50 so that the computer system cangenerate a translation matrix for correlation of the optical andelectromagnetic navigation system coordinates.

[0039] As illustrated in FIG. 5, showing a schematic version of adynamic translation device to be integrated one or more of the opticalelements 20 placed on the patient 30 (or mounted to the i patient via aframe), the electromagnetic element 90 is preferably a sensor asdescribed above with respect to FIG. 2. The sensor is preferably placedin or on the base 25 in known relation to the optical element 20. Theknown relation of the optical and electromagnetic elements is receivedby the computer system 50 so that the computer system can generate atranslation matrix for correlation of the optical and electromagneticnavigation system coordinates. Although the embodiment of FIG. 5 showsthe electromagnetic element being integrated with the optical element,the electromagnetic element may alternatively be attached to orinterchanged with the optical element 20 placed on the patient 30 (ormounted to the patient via a frame).

[0040] It is to be understood that an electromagnetic element 90 may beplaced on the patient 30 or on the medical instrument 60 for trackingmovement of the patient 30 and or the medical instrument 60 during theprocedure, even if the electromagnetic element 90 on the patient 30 andthe medical instrument 60 is not used as translation devices.

[0041] An exemplary operation of the system of the present inventionwill now be described. For the purposes of the example, the procedure isbrain surgery and the translation device is only included in the medicalinstrument 60, as illustrated in FIG. 2. An optical navigation systemand an electromagnetic navigation system are used.

[0042] Prior to the surgical procedure, fiducial markers are placed onthe patient's head and the patient's head is scanned using, for example,a MR, CT, ultrasound, fluoro or PET scanner. The scanner generates animage data set including data points corresponding to the fiducialmarkers.

[0043] The image data set is received and stored by the computer system.

[0044] After the patient's head has been scanned, the patient is placedon the operating table and the navigation systems are turned on. Inbrain surgery, the navigation systems track movement of the patientshead and movement of the medical instrument. Since the medicalinstrument is used as the translation device, both optical andelectromagnetic navigation system elements are placed on the medicalinstrument and both the optical and electromagnetic systems trackmovement of the medical instrument.

[0045] Since the patient's head must also be tracked, either optical orelectromagnetic navigation system elements must be placed on thepatient's head. For the purposes of the present illustration, opticalelements are placed on the patient's head. Since the optical navigationsystem is tracking movement of the patient's head, the opticalnavigation system's patient space must be registered to the image spacedefined by the pre-operative scan.

[0046] After the optical navigation system patient space has beenregistered to the image space, the electromagnetic navigation systempatient space must be registered to the optical navigation systempatient space. Having a known relation between the electromagnetic andoptical elements in the medical instrument allows the computer to use atranslation matrix to register the optical navigation system patientspace to the electromagnetic navigation system patient space. Thus, theelectromagnetic navigation patient space is registered to the imagespace.

[0047] If the medical instrument has a rigid design, knowing thedimensions of the medical instrument and the orientation and location ofthe localization frame 66 allows the computer system to determine theposition of the tip of the medical instrument. However, in the casewhere the medical instrument 60 has a non-rigid design, merely knowingthe location and orientation of the localization frame 66 by trackingthe position of the optical and electromagnetic elements cannot allowthe computer to determine the position of the tip 64 of the medicalinstrument. Additionally, optical navigation systems are line-of-sightnavigation systems and therefore do not allow direct tracking of the tipof a probe once it has been inserted into the patient (because the tipis out of the line-of sight of the optical receiving array).

[0048] However, electromagnetic navigation systems do not requireline-of-sight and therefore can track the location and orientation ofthe inserted tip of even a non-rigid medical instrument. To do so, anelectromagnetic element 90 is placed in the tip portion 64 of themedical instrument and is tracked by the electromagnetic navigationsystem. Since the electromagnetic navigation system patient space hasbeen registered to the image space, movement of the tip of the medicalinstrument within the patient's brain (within the image space) can betracked.

[0049] Thus, the present invention allows increased accuracy andflexibility for users by utilizing the features of multiple navigationsystem to their respective advantages. In addition, utilizing multiplenavigation systems often increases the overall working volume during theprocedure.

[0050] It will be apparent to those skilled in the art that variousmodifications and variations can be made to the system of the presentinvention without departing from the scope or spirit of the invention.Thus, it is intended that the present invention cover the modificationsand variations of this invention provided they come within the scope ofthe appended claims and their equivalents.

What is claimed is:
 1. A system for utilizing and registering at leasttwo surgical navigation systems during stereotactic surgery, the systemcomprising: a first surgical navigation system defining a first patientspace; a second surgical navigation system defining a second patientspace; and a translation device to register the coordinates of the firstpatient space to the coordinates of the second patient space.
 2. Thesystem of claim 1 , wherein the first navigation system is aline-of-sight navigation system.
 3. The system of claim 2 , wherein theline-of-sight navigation system is an optical navigation system.
 4. Thesystem of claim 2 , wherein the second navigation system is anon-line-of-sight navigation system.
 5. The system of claim 4 , whereinthe non-line-of sight system is an electromagnetic navigation system. 6.The system of claim 1 , wherein the translation device includes at leastone component for the first navigation system and at least one componentfor the second navigation system.
 7. The system of claim 6 , wherein thetranslation matrix between the at least one component for the firstnavigation system and the at least one component of the secondnavigation system is predetermined.
 8. The system of claim 7 , whereinthe first navigation system is an optical navigation system and the atleast one components for the first navigation system is an opticalelement.
 9. The system of claim 8 , wherein the second navigation systemis an electromagnetic navigation system and the at least one componentfor the second navigation system is an electromagnetic element.
 10. Thesystem of claim 9 , wherein the at least one electromagnetic element isa sensor.
 11. A device for registering coordinates of at least twonavigation systems, the device comprising: a rigid body; at least onecomponent for a first navigation system placed in or on the rigid body;and at least one component for a second navigation system placed in oron the rigid body, in known relation to the at least one component forthe first navigation system, wherein the device is positioned in aworking volume of each of the at least two navigation systems.
 12. Thedevice of claim 11 , wherein the first navigation system is a line-ofline-of-sight navigation system.
 13. The system of claim 12 , whereinthe line-of-sight navigation system is an optical navigation system. 14.The system of claim 12 , wherein the second navigation system is anon-line-of-sight navigation system.
 15. The system of claim 14 ,wherein the non-line-of sight system is an electromagnetic navigationsystem.
 16. The system of claim 11 , wherein the first navigation systemis an optical navigation system and the at least one component for thefirst navigation system is an optical element.
 18. The system of claim16 , wherein the second navigation system is an electromagneticnavigation system and the at least one component for the secondnavigation system is an electromagnetic element.
 19. The system of claim9 , wherein the electromagnetic element is a sensor.
 20. The system ofclaim 9 , wherein the electromagnetic element generates anelectromagnetic field.